JP4197696B2 - Natural circulation boiling water reactor - Google Patents

Natural circulation boiling water reactor Download PDF

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JP4197696B2
JP4197696B2 JP2005233750A JP2005233750A JP4197696B2 JP 4197696 B2 JP4197696 B2 JP 4197696B2 JP 2005233750 A JP2005233750 A JP 2005233750A JP 2005233750 A JP2005233750 A JP 2005233750A JP 4197696 B2 JP4197696 B2 JP 4197696B2
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divided
chimney
core
natural circulation
pressure
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JP2007047090A (en
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信明 安部
豊 武内
幸夫 瀧川
幹英 中丸
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C1/00—Reactor types
    • G21C1/04—Thermal reactors ; Epithermal reactors
    • G21C1/06—Heterogeneous reactors, i.e. in which fuel and moderator are separated
    • G21C1/08—Heterogeneous reactors, i.e. in which fuel and moderator are separated moderator being highly pressurised, e.g. boiling water reactor, integral super-heat reactor, pressurised water reactor
    • G21C1/084—Boiling water reactors
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C15/00—Cooling arrangements within the pressure vessel containing the core; Selection of specific coolants
    • G21C15/02—Arrangements or disposition of passages in which heat is transferred to the coolant; Coolant flow control devices
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C15/00—Cooling arrangements within the pressure vessel containing the core; Selection of specific coolants
    • G21C15/24—Promoting flow of the coolant
    • G21C15/26—Promoting flow of the coolant by convection, e.g. using chimneys, using divergent channels
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

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Description

本発明は、良好な自然循環特性を確保し、安全性を向上させた自然循環型沸騰水型原子炉に関する。   The present invention relates to a natural circulation boiling water nuclear reactor that secures good natural circulation characteristics and improves safety.

自然循環型沸騰水型原子炉（以下、自然循環型ＢＷＲという。）では、自然循環流量を確保するために、原子炉圧力容器を高くし、炉心を原子炉圧力容器内の相対的低い位置に設置し、炉心上部にチムニという大きな自由空間を形成している。   In a natural circulation boiling water reactor (hereinafter referred to as a natural circulation BWR), in order to ensure a natural circulation flow rate, the reactor pressure vessel is raised and the reactor core is placed at a relatively low position in the reactor pressure vessel. It is installed and a large free space called chimney is formed in the upper part of the core.

自然循環型ＢＷＲは、強制循環型の沸騰水型原子炉（ＢＷＲ）のように原子炉内再循環ポンプ（インターナルポンプ）や原子炉再循環系（原子炉外再循環ポンプおよびジェットポンプ）を備えず、原子炉内再循環ポンプ等で原子炉圧力容器内を強制循環させる構造となっていない。   The natural circulation type BWR is equipped with an in-reactor recirculation pump (internal pump) and a reactor recirculation system (external reactor recirculation pump and jet pump) like a forced circulation type boiling water reactor (BWR). It is not equipped with a structure that forcibly circulates in the reactor pressure vessel with a reactor recirculation pump or the like.

自然循環型ＢＷＲにおいては、原子炉圧力容器内で循環流路を形成する役割を果たしているシュラウド内外であるダウンカマ部および炉心部の密度差と炉心部の気液二相流の圧力損失のバランスで自然循環流量が決定される。この自然循環流量は、原子炉圧力容器を高くしてダウンカマ部の水頭圧（ヘッド）を大きくし、かつ炉心上部に大きな自由空間であるチムニを配置し、チムニでの気液二相流の圧力損失を低減させて水頭圧（ヘッド）を小さくし、シュラウド内外の密度差に基づく水頭圧差（ヘッド差）を大きくして確保される。   In the natural circulation type BWR, the balance between the density difference between the downcomer part and the core part inside and outside the shroud, which plays the role of forming the circulation channel in the reactor pressure vessel, and the pressure loss of the gas-liquid two-phase flow in the core part The natural circulation flow rate is determined. This natural circulation flow rate raises the reactor pressure vessel to increase the head pressure of the downcomer section, and a large free space chimney is placed at the top of the reactor core. The pressure of the gas-liquid two-phase flow at the chimney The loss is reduced, the head pressure (head) is reduced, and the head pressure difference (head difference) based on the density difference inside and outside the shroud is increased and secured.

炉心上部に構成されるチムニは、大型の自然循環型ＢＷＲでは、半径約５ｍ、高さ約１０ｍ程度にもなる非常に大きな自由空間である（特許文献１参照）。この自由空間を炉心上部に形成し、炉心から流出した気液二相流が流れる場合、大きな自由空間のチムニ内で多次元的な流れが発生し、自然循環流が阻害されることが考えられ、自然循環型ＢＷＲの開発で問題となっている。この多次元的な流れ現象は、ロシアの自然循環型ＢＷＲ Ｖｋ−５０で確認されている。   The chimney constructed in the upper part of the core is a very large free space having a radius of about 5 m and a height of about 10 m in a large natural circulation type BWR (see Patent Document 1). If this free space is formed in the upper part of the core and a gas-liquid two-phase flow that flows out of the core flows, a multidimensional flow is generated in the chimney of the large free space, and natural circulation flow may be hindered. This is a problem in the development of natural circulation BWRs. This multidimensional flow phenomenon has been confirmed in Russian natural circulation type BWR Vk-50.

また、炉心上部に設置されるチムニ内の熱流動挙動の解明のため、いわゆる大口径垂直配管内の気液二相流挙動試験がカナダのオンタリオハイドロ社で実施された。   In addition, a so-called gas-liquid two-phase flow behavior test in a so-called large-diameter vertical pipe was conducted at Ontario Hydro in Canada to elucidate the heat flow behavior in the chimney installed in the upper part of the core.

この気液二相流挙動試験は、口径約６０ｃｍの垂直配管を用いた高温高圧の試験であり、この試験により口径約６０ｃｍの垂直配管内の流れは、多次元ではなく、一次元的な安定した流れであることが判明した。   This gas-liquid two-phase flow behavior test is a high-temperature and high-pressure test using a vertical pipe with a caliber of about 60 cm, and the flow in the vertical pipe with a caliber of about 60 cm is not multidimensional but stable in one dimension. It turned out that it was the flow.

カナダの気液二相流挙動試験結果に基づき、大型の自然循環型沸騰水型原子炉、例えばＳＢＷＲでは、大きな自由空間であるチムニ領域に対して、気液二相流の安定した流れを確保するため、複数の４角格子板から構成される角筒状の分割チムニを採用している。分割チムニの大きさは、約６０ｃｍ四方であり、この大きさの角筒状の分割チムニであれば、カナダのオンタリオハイドロ社の試験結果のように、安定した自然循環流が確保される。   Based on Canadian gas-liquid two-phase flow behavior test results, large natural circulation boiling water reactors, such as SBWR, ensure stable flow of gas-liquid two-phase flow in the chimney region, which is a large free space. In order to do this, a rectangular tube-shaped divided chimney composed of a plurality of quadrangular lattice plates is employed. The size of the divided chimney is about 60 cm square, and the square chimney divided chimney of this size ensures a stable natural circulation flow as in the test results of Ontario Hydro of Canada.

自然循環型ＢＷＲでは、分割チムニを採用することにより、各分割チムニ内の流れが多次元的な流れでなく、一次元的な安定した流れとなり、安定した自然循環流量が確保できるようになった。   In the natural circulation type BWR, by adopting divided chimneys, the flow in each divided chimney is not a multi-dimensional flow, but a one-dimensional stable flow, and a stable natural circulation flow rate can be secured. .

分割チムニを採用した自然循環型原子炉として、特許文献２に開示された技術がある。この自然循環型原子炉は、分割チムニを採用することで良好な自然循環特性を確保するとともに、過渡時の水位低下を抑制している。この自然循環型ＢＷＲでは、分割チムニを上下に２分割し、上部の分割チムニの流路断面積が下部の分割チムニの流路断面積よりも小さくした分割チムニを採用している。   As a natural circulation nuclear reactor that employs divided chimneys, there is a technique disclosed in Patent Document 2. This natural circulation nuclear reactor uses split chimneys to ensure good natural circulation characteristics and to suppress a drop in water level during a transient. This natural circulation type BWR employs a divided chimney in which the divided chimney is vertically divided into two, and the channel sectional area of the upper divided chimney is smaller than the channel sectional area of the lower divided chimney.

分割チムニ領域を上下に２分割し、流路断面積を異にした分割チムニを採用することにより安定した自然循環流量が確保できる一方で、安定性が悪くなる虞がある。一般に、自然循環型ＢＷＲは安定性が悪いと言われている。   By adopting a divided chimney in which the divided chimney region is divided into two parts in the vertical direction and the cross-sectional areas of the flow paths are different, a stable natural circulation flow rate can be secured, but the stability may be deteriorated. In general, it is said that the natural circulation type BWR has poor stability.

安定性の観点から考察すると、沸騰水型原子炉（ＢＷＲ）の安定性には、チャンネル安定性、炉心安定性および領域安定性がある。このうち、チャンネル安定性は、燃料チャンネル（チャンネルボックス）内の圧力損失変化を介した熱流動フィードバックによる流量変動に関する熱水力的安定性である。炉心安定性と領域安定性は、炉心内のボイド変化による反応度変化を介した核的フィードバックによる中性子束振動の核熱水力的安定性である。また、炉心安定性は、炉心全体の出力が一体となって変動する中性子束の基本モードにおける安定性であり、領域安定性は、炉心出力の空間変動に伴う中性子束の高次モードの安定性である。   Considered from the viewpoint of stability, boiling water reactor (BWR) stability includes channel stability, core stability, and region stability. Among these, the channel stability is the thermo-hydraulic stability related to the flow rate fluctuation due to the heat flow feedback via the pressure loss change in the fuel channel (channel box). Core stability and region stability are the nuclear thermohydraulic stability of neutron flux oscillation by nuclear feedback via reactivity changes due to void changes in the core. Core stability is the stability in the fundamental mode of the neutron flux, where the power of the entire core fluctuates as a whole, and region stability is the stability of the higher order modes of the neutron flux associated with the spatial fluctuation of the core power. It is.

従来のＢＷＲは、多数の燃料集合体（燃料チャンネル）が装荷されて炉心が構成され、この炉心の上部および下部に共有のプレナム部を有して並行流路体系を形成している。多数の燃料チャンネルで並行流路体系を構成すると、特定の燃料チャンネルに流量変動が生じても、他の大多数の安定な燃料チャンネルの存在により、炉心の上下部のプレナム部間の圧力損失は一定に保たれる。   A conventional BWR is loaded with a large number of fuel assemblies (fuel channels) to form a core, and has a common plenum part at the top and bottom of the core to form a parallel flow path system. When a parallel flow path system is configured with a large number of fuel channels, the pressure loss between the plenums at the upper and lower parts of the core is reduced due to the presence of the majority of other stable fuel channels, even if flow fluctuations occur in a specific fuel channel. Kept constant.

並行流路体系の炉心では、特定の燃料チャンネル内が流量変動して圧力損失が変化しようとしても、この圧力損失を一定値に戻そうとする力が流体に作用する。チャンネル安定性は、上部プレナムおよび下部プレナムが炉心部共通の圧力境界として機能し、燃料チャンネル部の圧力損失が一定となるような境界条件下での単一な燃料チャンネルの安定性である。   In the core of the parallel flow path system, even if the flow loss fluctuates in a specific fuel channel and the pressure loss changes, a force for returning the pressure loss to a constant value acts on the fluid. Channel stability is the stability of a single fuel channel under boundary conditions where the upper and lower plenums function as a common pressure boundary in the core and the fuel channel pressure loss is constant.

ＢＷＲの燃料チャンネルは、垂直な加熱流路を形成しており、炉心部に流入した流体は沸騰によりボイドを発生し、炉心上部に向うに従ってボイド率が大きくなる炉心軸方向のボイド率分布を持つ気液二相流となるので、炉心入口流量の変化に対して、気液二相部の圧力損失は、ボイドの輸送遅れに伴う時間遅れをもって変化する。   The fuel channel of the BWR forms a vertical heating flow path, and the fluid flowing into the core generates voids by boiling and has a void ratio distribution in the core axis direction in which the void ratio increases toward the upper part of the core. Since it becomes a gas-liquid two-phase flow, the pressure loss in the gas-liquid two-phase portion changes with a time delay accompanying a void transport delay with respect to a change in the core inlet flow rate.

ＢＷＲの炉心部のように、気液二相部が存在する加熱流路においては、入口流量の変化に対して気液二相部の圧力損失は、ボイドの輸送遅れに伴う時間遅れをもって変化する。この時間遅れを伴う気液二相流の圧力損失変化がチャンネル安定性のフィードバックループのフィードバック量となる。一般的には、気液二相流の圧力損失の大きさが大きいほど、また、時間遅れが大きいほど、チャンネル安定性は不安定になる。   In the heating flow path where the gas-liquid two-phase part exists like the core part of the BWR, the pressure loss in the gas-liquid two-phase part changes with the time delay accompanying the void transport delay with respect to the change in the inlet flow rate. . The pressure loss change of the gas-liquid two-phase flow accompanied by this time delay becomes the feedback amount of the feedback loop of the channel stability. In general, the greater the pressure loss of the gas-liquid two-phase flow and the greater the time delay, the more unstable the channel stability.

自然循環型ＢＷＲの場合には、ＢＷＲの炉心部と異なり、炉心上部の圧力境界が分割チムニ出口となる。燃料チャンネルと分割チムニを一まとめにしたものとを仮想的に燃料チャンネルと考えると、チムニが無い場合に比べて気液二相流の領域が長くなり、ボイドのチムニ内での輸送遅れが付加されることとなる。このため、気液二相流の圧力損失や時間遅れが大きくなって仮想燃料チャンネルの安定性が悪化する虞がある。   In the case of the natural circulation type BWR, unlike the core part of the BWR, the pressure boundary at the upper part of the core is the divided chimney outlet. If the fuel channel and the divided chimney are collectively considered as the fuel channel, the gas-liquid two-phase flow area becomes longer than when there is no chimney, and the transport delay in the void chimney is added. Will be. For this reason, there is a risk that the pressure loss and time delay of the gas-liquid two-phase flow will increase and the stability of the virtual fuel channel will deteriorate.

分割チムニ付きの自然循環型ＢＷＲにおいて、燃料チャンネルの安定性の改善を目指した先行技術は存在しない。
特開平２−８０９９８号公報 特開平４−２５９８９４号公報 There is no prior art aiming at improving the stability of the fuel channel in a natural circulation BWR with divided chimneys.
Japanese Patent Laid-Open No. 2-80998 JP-A-4-259894

分割チムニ付きの自然循環型ＢＷＲでは、多次元的な流れが抑制されるので安定した一次元的流れとなって自然循環流量は確保されるが、燃料チャンネルと分割チムニを一まとめにしたものとを仮想的に燃料チャンネルと考えると、ＢＷＲの炉心に比べて気液二相流の領域が炉心軸方向に長くなり、ボイドのチムニ内での輸送遅れが付加され、仮想チャンネルの安定性が悪化する可能性がある。   In the natural circulation type BWR with split chimney, the multi-dimensional flow is suppressed, so a stable one-dimensional flow is ensured and the natural circulation flow rate is secured, but the fuel channel and the split chimney are combined. As a virtual fuel channel, the gas-liquid two-phase flow region becomes longer in the axial direction of the core than the BWR core, adding a transport delay in the void chimney and degrading the stability of the virtual channel. there's a possibility that.

従来のＢＷＲでは、図１３に示すように、各燃料集合体１内の圧力損失ΔＰが、炉心出口の上部プレナム部２において、炉心全体で均一となる条件でチャンネル安定性が評価されている。従来のＢＷＲの炉心３には、数百体の燃料集合体１が配置され、核燃料集合体１は炉心３に装荷されて並行流路を形成している。   In the conventional BWR, as shown in FIG. 13, the channel stability is evaluated under the condition that the pressure loss ΔP in each fuel assembly 1 is uniform in the entire core in the upper plenum portion 2 at the core outlet. Hundreds of fuel assemblies 1 are arranged in the core 3 of the conventional BWR, and the nuclear fuel assemblies 1 are loaded on the core 3 to form parallel flow paths.

並行流路を形成した炉心３部では、特定の燃料集合体（燃料チャンネル）１内で流体振動が生じても、その周辺の多くの燃料チャンネルに吸収され、炉心上部プレナム２と炉心下部プレナム４との間の各チャンネル差圧ΔＰ（ΔＰ１〜ΔＰＮ）は、ほぼ一定に保たれるフィードバック効果がチャンネル流量に対して作用する。 In the core 3 part in which the parallel flow paths are formed, even if fluid vibration occurs in a specific fuel assembly (fuel channel) 1, it is absorbed by many fuel channels around it, and the core upper plenum 2 and the core lower plenum 4. Each of the channel differential pressures ΔP (ΔP 1 to ΔP N ) has a feedback effect that is kept substantially constant, and acts on the channel flow rate.

チャンネル差圧ΔＰを一定に保つフィードバック効果が作用する過程で、燃料チャンネル内が気液二相状態であるため、流量変化から圧力損失変化に時間遅れが生じており、ある気液二相の条件下では燃料チャンネルに不安定性が生じることになる。気液二相状態の圧力損失変化から遅れ時間が大きい低流量や長流路の場合や、気液二相流の圧力損失変化が大きなゲインの場合には、安定性がより不安定となる。   In the process of the feedback effect that keeps the channel differential pressure ΔP constant, the fuel channel is in a gas-liquid two-phase state, so there is a time delay in the pressure loss change from the flow rate change. Below, instability will occur in the fuel channel. In the case of a low flow rate or a long flow path with a large delay time from the pressure loss change in the gas-liquid two-phase state, or in the case of a gain with a large pressure loss change in the gas-liquid two-phase flow, the stability becomes more unstable.

分割チムニ付き自然循環型ＢＷＲでは、図１４に示すように、分割チムニ６に流入する燃料チャンネルの圧力が炉心出口で一旦均圧化（差圧ΔＰＣ１〜ΔＰＣＮのＮ個の燃料チャンネル１内で均圧化）された後、全燃料チャンネル１の圧力がチムニ５出口で均圧化（差圧ΔＰＣＭ１〜ΔＰＣＭｋＰのｋ個の分割チムニ５間で均圧化）される。 In the natural circulation type BWR with divided chimneys, as shown in FIG. 14, the pressure of the fuel channel flowing into the divided chimney 6 is once equalized at the core outlet (in the N fuel channels 1 of the differential pressures ΔP C1 to ΔP CN ). Are equalized at the outlet of the chimney 5 (equalized between k divided chimneys 5 of differential pressures ΔP CM1 to ΔP CMk P).

このため、燃料集合体１と分割チムニ５を一まとめにしたものとを仮想的な燃料チャンネルと仮定すると、仮想燃料チャンネルは、従来のＢＷＲ炉心の燃料集合体１に比べ、分割チムニの軸方向長さ分だけ気液二相流領域の長さが長くなり、分割チムニ内でボイドによる輸送遅れが付加される。   For this reason, assuming that the fuel assembly 1 and the divided chimney 5 together are assumed to be a virtual fuel channel, the virtual fuel channel is more in the axial direction of the divided chimney than the fuel assembly 1 of the conventional BWR core. The length of the gas-liquid two-phase flow region is increased by the length, and a transport delay due to voids is added in the divided chimney.

このため、自然循環型ＢＷＲでは仮想燃料チャンネルのチャンネル安定性等の安定性が悪化する可能性がある。   For this reason, in natural circulation type BWR, stability, such as channel stability of a virtual fuel channel, may deteriorate.

本発明は、上述した事情を考慮してなされたもので、良好な自然循環特性を確保し、安定性を改善した自然循環型沸騰水型原子炉を提供することを目的とする。   The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a natural circulation boiling water nuclear reactor that ensures good natural circulation characteristics and has improved stability.

本発明に係る自然循環型沸騰水型原子炉は、上述した課題を解決するために、請求項１に記載したように、原子炉圧力容器の炉心シュラウド内において炉心上部に複数の分割チムニを備え、上記炉心に多数の燃料集合体を装荷した自然循環型沸騰水型原子炉において、前記炉心シュラウド内に設置された分割チムニの角筒状格子板に分割チムニ部を均圧にする構造を設け、この均圧化構造により、前記分割チムニ部を均圧化させたものである。   In order to solve the above-described problem, a natural circulation boiling water reactor according to the present invention includes a plurality of divided chimneys in an upper part of a core in a core shroud of a reactor pressure vessel as described in claim 1. In the natural circulation boiling water nuclear reactor in which a large number of fuel assemblies are loaded on the core, a structure is provided for equalizing the divided chimney portion on the square cylindrical lattice plate of the divided chimney installed in the core shroud. In this pressure equalizing structure, the divided chimney portion is pressure equalized.

また、本発明に係る自然循環型沸騰水型原子炉は、上述した課題を解決するために、請求項７に記載したように、原子炉圧力容器の炉心シュラウド内において炉心上部に複数の分割チムニを備え、上記炉心に多数の燃料集合体を装荷した自然循環型沸騰水型原子炉において、前記炉心シュラウド内に設置された前記分割チムニの領域をチムニ高さ方向に複数に分け、上部分割チムニ群の角筒状格子板を下部分割チムニ群の角筒状格子板より大きな横断面積を有するように構成し、前記分割チムニの高さ方向中間部で前記燃料集合体の間の圧力を均一化させたものである。   Further, in order to solve the above-described problem, the natural circulation boiling water reactor according to the present invention has a plurality of divided chimneys in the upper part of the core in the core shroud of the reactor pressure vessel as described in claim 7. A natural circulation boiling water reactor in which a large number of fuel assemblies are loaded in the core, and the divided chimney region installed in the core shroud is divided into a plurality of chimney height directions, and an upper divided chimney The square prismatic lattice plate of the group is configured to have a larger cross-sectional area than the square cylindrical lattice plate of the lower divided chimney group, and the pressure between the fuel assemblies is equalized at the middle part in the height direction of the divided chimney It has been made.

さらに、本発明に係る自然循環型沸騰水型原子炉は、上述した課題を解決するために、請求項９に記載したように、原子炉圧力容器の炉心シュラウド内において炉心上部に複数の分割チムニを備え、上記炉心に多数の燃料集合体を装荷した自然循環型沸騰水型原子炉において、前記炉心シュラウド内に設置された前記分割チムニの領域をチムニ高さ方向に複数に分け、上部分割チムニ群の角筒状格子板の中心位置を下部分割チムニ群の角筒状格子板の中心位置から横方向にシフトさせ、前記分割チムニの高さ方向中間部で燃料集合体の間を均圧化させたものである。   Furthermore, in order to solve the above-described problem, the natural circulation boiling water reactor according to the present invention has a plurality of divided chimneys in the upper part of the core in the core shroud of the reactor pressure vessel as described in claim 9. A natural circulation boiling water reactor in which a large number of fuel assemblies are loaded in the core, and the divided chimney region installed in the core shroud is divided into a plurality of chimney height directions, and an upper divided chimney The center position of the square cylindrical lattice plate of the group is shifted laterally from the central position of the rectangular cylindrical lattice plate of the lower divided chimney group, and the pressure between the fuel assemblies is equalized at the intermediate portion in the height direction of the divided chimney It has been made.

本発明に係る自然循環型沸騰水型原子炉は、炉心シュラウド内に設置された分割チムニの出口より上流側で分割チムニ部あるいは燃料集合体間の圧力を均圧化させることができて、安定性に重要な炉心上部の圧力境界位置を低下させることができる。気液二相流領域が短くなり、分割チムニ内の輸送遅れを解消でき、安定性の改善を図ることができる。   The natural circulation boiling water reactor according to the present invention is capable of equalizing the pressure between the divided chimney sections or the fuel assemblies upstream from the outlet of the divided chimney installed in the core shroud, and is stable. It is possible to reduce the pressure boundary position in the upper core, which is important for safety. The gas-liquid two-phase flow region is shortened, the transport delay in the divided chimney can be eliminated, and the stability can be improved.

本発明に係る自然循環型沸騰水型原子炉の実施の形態について添付図面を参照して説明する。   An embodiment of a natural circulation boiling water reactor according to the present invention will be described with reference to the accompanying drawings.

［第１実施形態］
図１は本発明に係る自然循環型沸騰水型原子炉（以下、自然循環型ＢＷＲという。）の第１実施形態を示す概念的な構成図である。この自然循環型ＢＷＲ１０は、原子炉圧力容器１１内に炉心シュラウド１２が設けられ、この炉心シュラウド１２内に数百体、例えば８００体程度の多数の燃料集合体１３を装架して炉心１４が構成される。炉心１４は炉心シュラウド１２の下部に設けられ、炉心１４の上方に角筒状の分割チムニ１５が複数設けられる。複数の分割チムニ１５を組み合せて分割チムニ群に組み立てられる。 [First Embodiment]
FIG. 1 is a conceptual configuration diagram showing a first embodiment of a natural circulation boiling water reactor (hereinafter referred to as a natural circulation BWR) according to the present invention. In this natural circulation type BWR 10, a core shroud 12 is provided in a reactor pressure vessel 11, and a large number of fuel assemblies 13, for example, about 800, are mounted in the core shroud 12, and a core 14 is provided. Composed. The core 14 is provided in the lower part of the core shroud 12, and a plurality of rectangular tubular divided chimneys 15 are provided above the core 14. A plurality of divided chimneys 15 are combined into a divided chimney group.

分割チムニ１５は複数個が束ねられてチムニ１６が構成され、各分割チムニ１５内部に自由空間をそれぞれ形成している。炉心１４は多数の燃料集合体１３を正方格子状に整列配置して炉心内に並列流路を構成している。炉心１４はその上部に分割チムニ１５群を有し、この炉心１４および分割チムニ１５群の上部および下部に共通のプレナム部１７，２８を有する並行流路体系を構成している。   A plurality of divided chimneys 15 are bundled to form a chimney 16, and a free space is formed in each divided chimney 15. The core 14 has a large number of fuel assemblies 13 arranged in a square lattice to form parallel flow paths in the core. The core 14 has a divided chimney 15 group at the upper part thereof, and constitutes a parallel flow path system having common plenum portions 17 and 28 at the upper and lower parts of the core 14 and the divided chimney 15 group.

チムニ１６の出口側に炉心上部プレナム１７が形成され、この上部プレナム１７はシュラウドヘッド１８で覆われている。シュラウドヘッド１８上には多数の気水分離器１９が林立状態で設置され、この気水分離器１９の上方に蒸気乾燥器２０が設けられる。蒸気乾燥器２０は気水分離器１９で気液分離された蒸気分から湿分を除去して乾燥させて乾き蒸気を形成し、この乾き蒸気を主蒸気として主蒸気管２１から図示しない蒸気タービンに供給されるようになっている。この主蒸気管２１は主蒸気系２２を構成している。   A core upper plenum 17 is formed on the outlet side of the chimney 16, and the upper plenum 17 is covered with a shroud head 18. A large number of steam separators 19 are installed on the shroud head 18 in a forested state, and a steam dryer 20 is provided above the steam separators 19. The steam dryer 20 removes moisture from the steam component separated by the gas-water separator 19 and dries it to form dry steam. This dry steam is converted into main steam from the main steam pipe 21 to a steam turbine (not shown). It comes to be supplied. The main steam pipe 21 constitutes a main steam system 22.

蒸気タービンで仕事をし、発電を行なうことで膨張した蒸気は復水器（図示せず）に排出され、この復水器で凝縮（冷却）されて復水となる。この復水は、復水給水系２４を通り、給水配管２５から給水として原子炉圧力容器１１内に還流されるようになっている。   The steam expanded by working with the steam turbine and generating electricity is discharged to a condenser (not shown), and condensed (cooled) by this condenser to become condensed water. This condensate passes through the condensate water supply system 24 and is recirculated into the reactor pressure vessel 11 from the water supply pipe 25 as water supply.

原子炉圧力容器１１に還流された給水は、気水分離器１９で気水分離された水分（戻り水）と混合されてダウンカマ部２７に案内される。ダウンカマ部２７は原子炉圧力容器１１と炉心シュラウド１２との間のスリーブ状あるいは円筒状の環状空間に形成され、給水と炉水の冷却材の混合流をダウンカマ部２７の上下部の水頭圧差を利用して自然循環流で下降させ、炉心１４下方の炉心下部プレナム２８に導くようになっている。   The water supplied to the reactor pressure vessel 11 is mixed with the water (returned water) separated by the steam separator 19 and guided to the downcomer 27. The downcomer portion 27 is formed in a sleeve-like or cylindrical annular space between the reactor pressure vessel 11 and the core shroud 12, and the water flow pressure difference between the upper and lower portions of the downcomer portion 27 is reduced by the mixed flow of coolant and reactor water coolant. It is lowered by a natural circulation flow and is guided to the core lower plenum 28 below the core 14.

ダウンカマ部２７を下降した混合流は、炉心下部プレナム２８で反転して上昇流となって炉心下部の入口に案内される。この混合流が炉心１４を通る間に核加熱作用を受けて加熱されて気液二相流となり、分割チムニ１５に流入せしめられる。この気液二相流は、その後炉心上部プレナム１７を上昇して気水分離器１９に導かれ、ここで気水分離される。   The mixed flow descending the downcomer portion 27 is reversed by the core lower plenum 28 to be converted into an upward flow and guided to the inlet at the lower core. While this mixed flow passes through the core 14, it receives a nuclear heating action and is heated to become a gas-liquid two-phase flow and flows into the divided chimney 15. The gas-liquid two-phase flow then moves up the core upper plenum 17 and is guided to the steam separator 19 where the steam is separated.

一方、原子炉圧力容器１１内に収容される炉心シュラウド１２内の下部には多数の燃料集合体１３を装荷した炉心１４が形成され、この炉心１４の上部に角筒状分割チムニ１５が設けられる。分割チムニ１５は格子板３０を角筒状に構成して内部に自由空間を形成している。分割チムニ１５は隣り合う分割チムニ１５と均圧管３１で連絡され、この均圧管３１を介して隣り合う分割チムニ１５内の圧力が均一となるように調節される。均圧管３１は分割チムニ１５の軸方向高さの中間領域より下方に設けられ、分割チムニ１５部の圧力均圧構造を構成している。角筒状の分割チムニ１５は約６０ｃｍ四方の大きさで軸方向高さが数ｍ〜１０数ｍの高さ、例えば１０ｍの高さとなるように設けられる。チムニ１６は一例として全体の口径、分割チムニ１５の合計口径が約５ｍ、軸方向高さが１０ｍとなるように構成される。   On the other hand, a core 14 loaded with a large number of fuel assemblies 13 is formed in the lower part of the core shroud 12 accommodated in the reactor pressure vessel 11, and a rectangular tube-shaped divided chimney 15 is provided on the upper part of the core 14. . The divided chimney 15 has a lattice plate 30 formed in a square tube shape to form a free space therein. The divided chimney 15 is connected to the adjacent divided chimney 15 by the pressure equalizing pipe 31, and the pressure in the adjacent divided chimney 15 is adjusted to be uniform through the pressure equalizing pipe 31. The pressure equalizing pipe 31 is provided below an intermediate region of the axial height of the divided chimney 15 and constitutes a pressure equalizing structure of the divided chimney 15 portion. The rectangular cylindrical chimney 15 has a size of about 60 cm square and an axial height of several m to several tens m, for example, 10 m. As an example, the chimney 16 is configured such that the overall aperture, the total aperture of the divided chimneys 15 is about 5 m, and the axial height is 10 m.

また、炉心１４を構成する燃料集合体１３は角筒状のチャンネルボックス３３内に多数の燃料棒が正方格子状に整列配置されて収納される。多数の燃料集合体１３間に制御棒３４が図示しない制御棒駆動装置により出し入れされて炉出力が調節される。制御棒３４は横断面十字形をなして４体１組の燃料集合体１３間に出し入れ調節制御される。   The fuel assembly 13 constituting the core 14 is accommodated in a rectangular tube channel box 33 in which a large number of fuel rods are arranged in a square lattice. A control rod 34 is inserted into and removed from a large number of fuel assemblies 13 by a control rod driving device (not shown) to adjust the furnace output. The control rod 34 has a cross-shaped cross section and is controlled to be inserted and removed between the four fuel assemblies 13.

炉心１４上方に隣接して設置される各分割チムニ１５は、図２に示すように、均圧管３１で連絡して隣り合う分割チムニ１５内の空間圧力が均一となるように調節される。   As shown in FIG. 2, each divided chimney 15 installed adjacent to the upper part of the core 14 is connected by a pressure equalizing pipe 31 and adjusted so that the space pressure in the adjacent divided chimney 15 becomes uniform.

分割チムニ１５間の圧力を均一にするための圧力均圧化構造は、均圧管３１を設ける代りに、分割チムニ１５の入口部近傍に連絡孔３５を、図３に示すように設けてもよい。連絡孔３５は、円形、楕円形、長円形あるいは矩形形状に形成され、角筒状の分割チムニ１５入口部の格子板３０の各板面に対応してそれぞれ設置される。   In the pressure equalizing structure for making the pressure between the divided chimneys 15 uniform, instead of providing the pressure equalizing pipe 31, a communication hole 35 may be provided in the vicinity of the inlet portion of the divided chimney 15 as shown in FIG. . The communication hole 35 is formed in a circular shape, an elliptical shape, an oval shape, or a rectangular shape, and is installed in correspondence with each plate surface of the lattice plate 30 at the entrance portion of the rectangular chimney 15.

この実施形態に示された自然循環型ＢＷＲ１０では原子炉圧力容器１１内に多数の燃料集合体１３を収容して炉心シュラウド１２内下部に炉心１４を形成し、各燃料集合体１３の出口側に分割チムニ１５を束ねた分割チムニ群を設ける。   In the natural circulation type BWR 10 shown in this embodiment, a large number of fuel assemblies 13 are accommodated in a reactor pressure vessel 11 and a core 14 is formed in the lower portion of the core shroud 12, and at the outlet side of each fuel assembly 13. A divided chimney group in which the divided chimneys 15 are bundled is provided.

隣り合う分割チムニ１５は均圧管３１により、また、各分割チムニ１５に形成された連絡孔３５により、分割チムニ部の圧力を均一化させることができる。すなわち、炉心１４を構成する燃料集合体１３出口の分割チムニ部で全燃料集合体１３間で均圧化することができる。   Adjacent divided chimneys 15 can equalize the pressure in the divided chimney portions by pressure equalizing pipes 31 and by communication holes 35 formed in each divided chimney 15. That is, the pressure can be equalized among all the fuel assemblies 13 at the divided chimney portion at the outlet of the fuel assembly 13 constituting the core 14.

これにより、燃料チャンネルのチャンネル安定性に重要である炉心上部の圧力境界が分割チムニ１５出口から分割チムニ１５入口側の連絡孔３５あるいは均圧管３１となって気液二相流領域が短くなり、分割チムニ１５内の輸送遅れがなくなり、あるいは、この輸送遅れを大幅に改善できるので、安定性を改善することができる。   As a result, the pressure boundary at the upper part of the core, which is important for the channel stability of the fuel channel, changes from the divided chimney 15 outlet to the connecting hole 35 or the pressure equalizing pipe 31 on the divided chimney 15 inlet side, and the gas-liquid two-phase flow region is shortened. Since the transport delay in the divided chimney 15 is eliminated or the transport delay can be greatly improved, the stability can be improved.

［第１実施形態の変形例］
図４は、本発明に係る自然循環型ＢＷＲの第１実施形態の第１変形例を示すものである。 [Modification of First Embodiment]
FIG. 4 shows a first modification of the first embodiment of the natural circulation type BWR according to the present invention.

この第１変形例に示された分割チムニ１５Ａは、図２および図３に示した分割チムニ１５と構成を異にし、他の構成および作用は図１に示された自然循環型ＢＷＲ１０と異ならないので同一部材には同じ符号を付して図示ならびに説明を省略する。   The divided chimney 15A shown in the first modified example has a different configuration from the divided chimney 15 shown in FIGS. 2 and 3, and other configurations and operations are not different from the natural circulation type BWR 10 shown in FIG. Therefore, the same reference numerals are assigned to the same members, and illustration and description are omitted.

図４に示された分割チムニ１５Ａは、角筒状の各格子板３０の各板面下部に複数個の連絡孔３６ａ，３６ｂを上下方向にそれぞれ形成したものである。   The divided chimney 15A shown in FIG. 4 is formed by forming a plurality of connecting holes 36a, 36b in the vertical direction at the lower part of each plate surface of each square-plate-like lattice plate 30.

また、図５は、本発明に係る自然循環型ＢＷＲの第１実施形態における第２変形例を示すものである。   FIG. 5 shows a second modification of the first embodiment of the natural circulation BWR according to the present invention.

この第２変形例に示された分割チムニ１５Ｂは、角筒状の各格子板３０にチムニ軸方向に延びるスリット３７をそれぞれ形成したものである。図５では縦スリット３７を形成した例を示したが、横スリットを角筒状格子板３０のチムニ軸方向に多段に形成してもよい。   The divided chimney 15B shown in the second modification is formed by forming slits 37 extending in the chimney axial direction in each square-plate-shaped lattice plate 30. Although FIG. 5 shows an example in which the vertical slits 37 are formed, the horizontal slits may be formed in multiple stages in the chimney axis direction of the square cylindrical lattice plate 30.

さらに、図６は、本発明に係る自然循環型ＢＷＲの第１実施形態における第３変形例を示すものである。   FIG. 6 shows a third modification of the first embodiment of the natural circulation BWR according to the present invention.

この第３変形例に示された自然循環型ＢＷＲ１０は、各分割チムニ１５に連絡孔３５；３６ａ，３６ｂやスリット３７を形成する代りに、炉心１４を構成する燃料集合体１３群の上部と分割チムニ１５の入口（下部）との間に隙間３８を形成したものである。   The natural circulation type BWR 10 shown in the third modification is divided into the upper part of the fuel assembly 13 group constituting the core 14 instead of forming the communication holes 35; 36a, 36b and the slits 37 in each divided chimney 15. A gap 38 is formed between the inlet (lower part) of the chimney 15.

自然循環型ＢＷＲ１０では、燃料集合体１３群の上部に設けられる分割チムニ１５に均圧管３１を設け、この均圧管３１で隣り合う分割チムニ１５，１５同士を連通したり、また、燃料集合体１３群の上部に設置される角筒状の各分割チムニ１５の角筒状の格子板３０に、１つ以上の連絡孔３５；３６ａ，３６ｂを設けたり、スリット３７を設けたり、さらに、燃料集合体１３群の上部と分割チムニ１５群の下部との間に隙間３８を設けることにより、燃料集合体１３出口の分割チムニ１５部で全燃料集合体１３間を均圧化することができる。複数の連絡孔３６ａ，３６ｂは分割チムニ１５のチムニ軸方向下部側に設けられる一方、スリット３７は分割チムニ１５の格子板３０の中間部下方から下部にかけて穿設される。スリット３７は縦方向に形成する代りに、横方向（幅方向）に１段以上形成するようにしてもよい。   In the natural circulation type BWR 10, a pressure equalizing pipe 31 is provided in a divided chimney 15 provided in the upper part of the group of fuel assemblies 13, and the adjacent divided chimneys 15, 15 are communicated with each other by the pressure equalizing pipe 31. One or more connecting holes 35; 36a, 36b, slits 37, a fuel assembly, and the like are provided in the rectangular cylindrical lattice plate 30 of each rectangular cylindrical chimney 15 installed in the upper part of the group. By providing the gap 38 between the upper part of the body 13 group and the lower part of the divided chimney 15 group, it is possible to equalize the pressure between all the fuel assemblies 13 at the divided chimney 15 part at the outlet of the fuel assembly 13. The plurality of communication holes 36 a and 36 b are provided on the lower side in the chimney axial direction of the divided chimney 15, while the slit 37 is formed from the lower part to the lower part of the lattice plate 30 of the divided chimney 15. Instead of forming the slits 37 in the vertical direction, one or more steps may be formed in the horizontal direction (width direction).

全燃料集合体１３，１３間を分割チムニ１５部で均圧化することにより、燃料チャンネルのチャンネル安定性に重要である炉心上部の圧力境界が分割チムニ１５の出口側から分割チムニ１５の略入口側に下降させて形成することが可能となって気液二相流領域を短くすることができる。これにより、分割チムニ１５群の輸送遅れがなくなるので、チャンネル安定性等の安定性の改善を図ることができる。   By equalizing the pressure between all the fuel assemblies 13 and 15 with the divided chimney 15 part, the pressure boundary at the upper part of the core, which is important for the channel stability of the fuel channel, is substantially the inlet of the divided chimney 15 from the outlet side of the divided chimney 15. Therefore, the gas-liquid two-phase flow region can be shortened. Thereby, since the transport delay of the divided chimney 15 group is eliminated, stability such as channel stability can be improved.

［第２実施形態］
図７および図８は本発明に係る自然循環型ＢＷＲの第２実施形態を示す図である。 [Second Embodiment]
7 and 8 are views showing a second embodiment of the natural circulation type BWR according to the present invention.

図７は、自然循環型ＢＷＲの第２実施形態を示す概略的な縦断面図、図８は図７のＶＩＩＩ−ＶＩＩＩ線に沿う平断面図である。   FIG. 7 is a schematic longitudinal sectional view showing a second embodiment of the natural circulation type BWR, and FIG. 8 is a plan sectional view taken along the line VIII-VIII of FIG.

第２実施形態に示された自然循環型ＢＷＲ１０Ａにおいて、第１実施形態に示された自然循環型ＢＷＲ１０と同じ構成には、同一符号を付して説明を省略する。   In the natural circulation type BWR 10A shown in the second embodiment, the same components as those in the natural circulation type BWR 10 shown in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

図７に示された自然循環型ＢＷＲ１０Ａは、炉心１４を構成する燃料集合体１３群の上部に複数の角筒状の分割チムニ１５を束ねて設置し、分割チムニ群からなるチムニ１６を構成している。   In the natural circulation BWR 10A shown in FIG. 7, a plurality of rectangular tube-shaped divided chimneys 15 are bundled and installed on the upper part of the fuel assembly 13 group constituting the core 14 to constitute a chimney 16 composed of divided chimney groups. ing.

チムニ１６を構成する各分割チムニ１５は、最外周に配設された分割チムニ１５の角筒状格子板４０に少なくとも１つの連絡孔４１を設ける。最外周領域に配設される隣り合う分割チムニ１５の各格子板４０の連絡孔４１の口径は、最外周領域以外の中央側領域の分割チムニ１５の格子板４３に形成された少なくとも１つの連絡孔４４の口径よりも大きくし、チャンネル流量が少なくかつ炉出力が大きく異なる周辺部の燃料集合体１３間の圧力を均圧化するものである。   Each divided chimney 15 constituting the chimney 16 is provided with at least one communication hole 41 in the square cylindrical lattice plate 40 of the divided chimney 15 disposed on the outermost periphery. The diameter of the communication hole 41 of each lattice plate 40 of adjacent divided chimneys 15 disposed in the outermost peripheral region is at least one communication formed in the lattice plate 43 of the divided chimney 15 in the central region other than the outermost peripheral region. It is larger than the diameter of the hole 44, and equalizes the pressure between the peripheral fuel assemblies 13 with a small channel flow rate and greatly different furnace power.

第２実施形態の自然循環型ＢＷＲ１０Ａにおいては、炉出力が大きく異なる原子炉圧力容器１１内炉心１４の周辺部の各燃料集合体１３内および各燃料集合体１３間の圧力を均圧化することができる。   In the natural circulation type BWR 10A of the second embodiment, the pressure in the fuel assemblies 13 and between the fuel assemblies 13 at the periphery of the core 14 in the reactor pressure vessel 11 having greatly different reactor outputs is equalized. Can do.

この結果、安定性に重要な炉心上部圧力境界位置を分割チムニ１５の各連絡孔４１，４４形成位置まで下げることができ、気液二相流の流れが短くなり、分割チムニ１５内の輸送遅れがなくなるので、安定性を改善することができる。   As a result, the core upper pressure boundary position, which is important for stability, can be lowered to the positions where the respective communication holes 41, 44 of the divided chimney 15 are formed, the flow of the gas-liquid two-phase flow is shortened, and the transport delay in the divided chimney 15 is reduced. The stability can be improved.

分割チムニ１５に形成される各連絡孔４１，４４は、燃料集合体１３の外周部に対応する分割チムニ１５の最外周部の各連絡孔４１が残りの分割チムニ１５の各連絡孔４４より大きな径に形成される。各連絡孔４１，４４は、分割チムニ１５の格子板４０，４３の適宜位置に１個以上形成される。各連絡孔４１，４４の孔形状は、円形であっても、矩形であっても、楕円や長円形であっても、また、スリット形状であってもよい。   The communication holes 41, 44 formed in the divided chimney 15 are larger than the communication holes 44 of the remaining divided chimneys 15, where the communication holes 41 in the outermost peripheral part of the divided chimney 15 corresponding to the outer peripheral part of the fuel assembly 13 are larger. Formed in diameter. One or more communication holes 41 and 44 are formed at appropriate positions on the lattice plates 40 and 43 of the divided chimney 15. The hole shape of each communication hole 41, 44 may be circular, rectangular, elliptical, oval, or slit-shaped.

また、各分割チムニ１５の連絡孔４１，４４は、好ましくはチムニ軸方向において中央部より下部側に対応して形成される。各連絡孔４１，４４は、分割チムニ１５角筒状の各格子板４０，４３の適宜位置に、または各格子板４０，４３の板面全体に上下方向に沿って複数個形成してもよい。いずれにしても各分割チムニ１５に形成される各連絡孔４１，４４は、それぞれ少なくとも１つが燃料集合体１３群の出口側近くに形成され、炉心上部の圧力境界位置が炉心上部プレナム１７より下方位置に形成されるように配慮している。   Further, the communication holes 41 and 44 of each divided chimney 15 are preferably formed so as to correspond to the lower side of the center part in the chimney axis direction. A plurality of the communication holes 41 and 44 may be formed along the vertical direction at appropriate positions of the grid plates 40 and 43 in the divided chimney 15-square tube shape or on the entire plate surfaces of the grid plates 40 and 43. . In any case, at least one of the communication holes 41 and 44 formed in each divided chimney 15 is formed near the outlet side of the fuel assembly 13 group, and the pressure boundary position of the upper core is below the upper plenum 17 of the core. Care is taken to form the position.

［第３実施形態］
図９および図１０は、本発明に係る自然循環型ＢＷＲの第３実施形態を示す図である。 [Third Embodiment]
9 and 10 are diagrams showing a third embodiment of the natural circulation BWR according to the present invention.

図９は、自然循環型ＢＷＲ１０Ｂの第３実施形態を示す概略的な縦断面図、図１０は、図９のＢ部を拡大して示し、かつ炉心部および分割チムニ１５の軸方向高さと炉圧力との関係を示す図である。   FIG. 9 is a schematic longitudinal sectional view showing a third embodiment of the natural circulation type BWR 10B. FIG. 10 is an enlarged view of a portion B in FIG. 9, and the axial height of the core portion and the divided chimney 15 and the reactor. It is a figure which shows the relationship with a pressure.

第３実施形態に示された自然循環型ＢＷＲ１０Ｂにおいて、第１実施形態に示された自然循環型ＢＷＲ１０と同じ構成には、同一符号を付して説明を省略する。   In the natural circulation type BWR 10B shown in the third embodiment, the same components as those in the natural circulation type BWR 10 shown in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

図９に示された自然循環型ＢＷＲ１０Ｂは、原子炉圧力容器１１内において炉心１４上部に形成されるチムニ１６が分割チムニ領域５０，５１をチムニ高さ方向に複数領域に分けられる。図９ではチムニ１６の軸方向上下に分割チムニ領域５０，５１を２分割したものである。   In the natural circulation type BWR 10B shown in FIG. 9, the chimney 16 formed on the upper portion of the core 14 in the reactor pressure vessel 11 is divided into a plurality of divided chimney regions 50 and 51 in the chimney height direction. In FIG. 9, the divided chimney regions 50 and 51 are divided into two in the axial direction of the chimney 16.

上部分割チムニ領域５０を構成する角筒状の分割チムニ５２群は、下部チムニ領域５１を構成する角筒状分割チムニ５３群より、分割チムニ格子板の枚数を少なくし、上部分割チムニ５２の横断面積を、複数、例えば４個の下部分割チムニ５３の合計横断面積とほぼ等しく形成される。 In the rectangular tube-shaped divided chimney 52 group constituting the upper divided chimney region 50, the number of divided chimney lattice plates is smaller than that of the rectangular tube-shaped divided chimney 53 group constituting the lower chimney region 51, and the upper divided chimney 52 is crossed. The area is formed substantially equal to the total cross-sectional area of a plurality of, for example, four lower divided chimneys 53.

チムニ１６は平面視において、上部分割チムニ５２の横断面積が複数、例えば４個の下部分割チムニ５３の合計横断面積とほぼ等しく、上部および下部分割チムニ５２，５３の境界位置が、従来の分割チムニの出口より下方になるように設定される。   In the plan view, the chimney 16 has a cross-sectional area of the upper divided chimney 52 that is substantially equal to the total cross-sectional area of a plurality of, for example, four lower divided chimneys 53, and the boundary positions of the upper and lower divided chimneys 52 and 53 are It is set so that it is below the exit.

上下の分割チムニ領域５０，５１をチムニ高さ方向（チムニ軸方向）に複数に分け、１つの上部分割チムニ５２が複数の下部分割チムニ５３と横断面積において等価に構成することにより、分割チムニ５２，５３の上流側で、図１０に示すように、燃料集合体１３間の圧力（炉圧力）を均一化させることができる。   The upper and lower divided chimney regions 50 and 51 are divided into a plurality of chimney height directions (chimney axis directions), and one upper divided chimney 52 is configured to be equivalent to a plurality of lower divided chimneys 53 in the cross-sectional area. , 53, the pressure (furnace pressure) between the fuel assemblies 13 can be made uniform as shown in FIG.

この結果、安定性に重要な炉心上部の圧力境界位置を低下させることができる。炉心上部の圧力境界位置を従来の自然循環型ＢＷＲの分割チムニ出口位置より下方に下げることができ、気液二相流領域が短くなる。このため、分割チムニ内の輸送遅れを解消することができ、チャンネル安定性等の安定性を改善することができる。   As a result, the pressure boundary position in the upper part of the core, which is important for stability, can be lowered. The pressure boundary position in the upper part of the core can be lowered below the divided chimney exit position of the conventional natural circulation type BWR, and the gas-liquid two-phase flow region is shortened. For this reason, the transport delay in the division | segmentation chimney can be eliminated, and stability, such as channel stability, can be improved.

［第３実施形態の変形例］
図１１および図１２は、自然循環型ＢＷＲの第３実施形態における変形例を示す図である。 [ Modification of Third Embodiment]
FIG. 11 and FIG. 12 are diagrams showing a modification of the third embodiment of the natural circulation type BWR.

図１１は、自然循環型ＢＷＲ１０Ｂの第３実施形態の変形例を示す概略的な縦断面図であり、図１２は、図１１のＣ部を拡大して示す斜視図である。   FIG. 11 is a schematic longitudinal sectional view showing a modified example of the third embodiment of the natural circulation type BWR 10B, and FIG. 12 is an enlarged perspective view showing a portion C of FIG.

この変形例を説明するに当たり、第３実施形態に示された自然循環型ＢＷＲ１０Ｂと同じ構成は、同一符号を付して説明を省略する。この変形例に示された自然循環型ＢＷＲ１０Ｂは、炉心１４上部に設けられるチムニ１６の上下分割構造を、図９および図１０のチムニの上下分割構造と異にする。   In describing this modification, the same components as those of the natural circulation type BWR 10B shown in the third embodiment are denoted by the same reference numerals, and description thereof is omitted. In the natural circulation type BWR 10B shown in this modification, the upper and lower divided structure of the chimney 16 provided in the upper part of the core 14 is different from the upper and lower divided structure of the chimney of FIGS.

変形例に示された自然循環型ＢＷＲ１０Ｂにおいても、複数の燃料集合体１３の上部に形成される分割チムニ領域５６，５７をチムニ高さ方向に複数、例えば２つの分割チムニ領域に分け、角筒状の上部分割チムニ５８と同じく角筒状の下部分割チムニ５９の中心位置を炉心１４の径方向、具体的には水平方向にシフトさせたものである。炉心径方向へのシフト量は、分割チムニ５９の１個当たりの幅寸法の範囲内で適宜設定される。   Also in the natural circulation type BWR 10B shown in the modified example, the divided chimney regions 56 and 57 formed on the upper portions of the plurality of fuel assemblies 13 are divided into a plurality of, for example, two divided chimney regions in the chimney height direction. Similar to the upper divided chimney 58, the center position of the rectangular lower divided chimney 59 is shifted in the radial direction of the core 14, more specifically in the horizontal direction. The shift amount in the core radial direction is appropriately set within the range of the width dimension of each divided chimney 59.

この変形例の自然循環型ＢＷＲ１０Ｂは、上部分割チムニ８の角筒状格子板６０と下部分割チムニ５９の角筒状格子板６１の中心位置をずらすことにより、上部分割チムニ５８出口より上流側で燃料集合体１３間の圧力を均圧化させることができる。   The natural circulation type BWR 10B of this modified example is located upstream of the outlet of the upper divided chimney 58 by shifting the center positions of the rectangular cylindrical lattice plate 60 of the upper divided chimney 8 and the rectangular cylindrical lattice plate 61 of the lower divided chimney 59. The pressure between the fuel assemblies 13 can be equalized.

このように、チムニ１６の出口より上流側で燃料集合体１３間の圧力を均圧化させることができるので、安定性に重要な炉心上部の圧力境界位置を下方に下げることができ、気液二相流領域が短くなるので、分割チムニ５８，５９内の輸送遅れを解消することができ、安定性を改善することができる。   In this way, the pressure between the fuel assemblies 13 can be equalized upstream from the outlet of the chimney 16, so that the pressure boundary position at the upper part of the core, which is important for stability, can be lowered downward. Since the two-phase flow region is shortened, the transport delay in the divided chimneys 58 and 59 can be eliminated, and the stability can be improved.

本発明に係る自然循環型ＢＷＲの第１実施形態を示す概略的な縦断面図。1 is a schematic longitudinal sectional view showing a first embodiment of a natural circulation type BWR according to the present invention. 図１のＡ部を拡大して示す斜視図、ならびに高さと圧力との関係を示す図。The perspective view which expands and shows the A section of FIG. 1, and the figure which shows the relationship between height and a pressure. 図１に示された自然循環型ＢＷＲに備えられる分割チムニを示す斜視図。The perspective view which shows the division | segmentation chimney with which the natural circulation type BWR shown by FIG. 1 is equipped. 自然循環型ＢＷＲに備えられる分割チムニの第１変形例を示す斜視図。The perspective view which shows the 1st modification of the division | segmentation chimney with which natural circulation type BWR is equipped. 自然循環型ＢＷＲに備えられる分割チムニの第２変形例を示す斜視図。The perspective view which shows the 2nd modification of the division | segmentation chimney with which natural circulation type BWR is equipped. 自然循環型ＢＷＲに備えられる分割チムニの第３変形例を示すもので自然循環型ＢＷＲの簡略的な縦断面図。The simplified longitudinal cross-sectional view of a natural circulation type BWR which shows the 3rd modification of the division | segmentation chimney with which natural circulation type BWR is equipped. 本発明に係る自然循環型ＢＷＲの第２実施形態を概略的に示す縦断面図。The longitudinal section showing roughly a 2nd embodiment of natural circulation type BWR concerning the present invention. 図７のＶＩＩＩ−ＶＩＩＩ線に沿う平断面図。FIG. 8 is a plan sectional view taken along line VIII-VIII in FIG. 7. 本発明に係る自然循環型ＢＷＲの第３実施形態を概略的に示す縦断面図。The longitudinal cross-sectional view which shows 3rd Embodiment of the natural circulation type BWR which concerns on this invention roughly. 図９のＢ部を拡大して示す斜視図、ならびに高さと圧力との関係を示す図。The perspective view which expands and shows the B section of FIG. 9, and the figure which shows the relationship between height and a pressure. 本発明に係る自然循環型ＢＷＲの第３実施形態の変形例を概略的に示す縦断面図。The longitudinal cross-sectional view which shows roughly the modification of 3rd Embodiment of the natural circulation type BWR which concerns on this invention. 図１１のＣ部を拡大して示す斜視図。The perspective view which expands and shows the C section of FIG. 従来の沸騰水型原子炉のチャンネル安定性を示す解説図。An explanatory diagram showing the channel stability of a conventional boiling water reactor. 分割チムニ付きの自然循環型ＢＷＲのチャンネル安定性を示す解説図。Explanatory drawing which shows the channel stability of natural circulation type BWR with a division chimney.

符号の説明Explanation of symbols

１０ 自然循環型沸騰水型原子炉
１１ 原子炉圧力容器
１２ 炉心シュラウド
１３ 燃料集合体
１４ 炉心
１５ 分割チムニ
１６ チムニ
１７ 炉心上部プレナム
１８ シュラウドヘッド
１９ 気水分離器（セパレータ）
２０ 蒸気乾燥器
２１ 主蒸気管
２２ 主蒸気系
２４ 復水給水系
２５ 給水配管
２７ ダウンカマ部
２８ 炉心下部プレナム
３０ 格子板
３１ 均圧管
３３ チャンネルボックス
３４ 制御棒
３５ 連絡孔
３６ａ，３６ｂ 連絡孔
３７ スリット
３８ 隙間
４０，４３ 格子板
４１，４４ 連絡孔
５０，５１，５６，５７ 分割チムニ領域
５２，５３，５８，５９ 分割チムニ
５４，５５，６０，６１ 分割チムニ格子板 DESCRIPTION OF SYMBOLS 10 Natural circulation type boiling water reactor 11 Reactor pressure vessel 12 Core shroud 13 Fuel assembly 14 Core 15 Split chimney 16 Chimney 17 Core upper plenum 18 Shroud head 19 Air-water separator (separator)
20 steam dryer 21 main steam pipe 22 main steam system 24 condensate water supply system 25 water supply pipe 27 downcomer section 28 core lower plenum 30 lattice plate 31 pressure equalizing pipe 33 channel box 34 control rod 35 connecting holes 36a, 36b connecting hole 37 slit 38 Gap 40, 43 Grid plate 41, 44 Connecting hole 50, 51, 56, 57 Divided chimney region 52, 53, 58, 59 Divided chimney 54, 55, 60, 61 Divided chimney grid plate

Claims (10)

原子炉圧力容器の炉心シュラウド内において炉心上部に複数の分割チムニを備え、上記炉心に多数の燃料集合体を装荷した自然循環型沸騰水型原子炉において、前記炉心シュラウド内に設置された分割チムニの角筒状格子板に分割チムニ部を均圧にする構造を設け、この均圧化構造により、前記分割チムニ部を均圧化させたことを特徴とする自然循環型沸騰水型原子炉。 In a natural circulation boiling water nuclear reactor having a plurality of divided chimneys in the upper part of the core in the core shroud of the reactor pressure vessel and loaded with a number of fuel assemblies in the core, the divided chimneys installed in the core shroud A natural-circulation boiling water nuclear reactor in which a structure for equalizing the divided chimney portion is provided on the square cylindrical lattice plate, and the divided chimney portion is equalized by the pressure equalizing structure. 前記均圧化構造は、前記分割チムニの格子板の板面に１個以上の連絡孔を設けて構成し、上記分割チムニの連絡孔により分割チムニ部を均圧化させた請求項１記載の自然循環型沸騰水型原子炉。 2. The pressure equalization structure according to claim 1, wherein one or more connecting holes are provided in a plate surface of the lattice plate of the divided chimney, and the divided chimney portion is pressure-equalized by the connecting hole of the divided chimney. Natural circulation boiling water reactor. 前記均圧化構造は、前記分割チムニの格子板の板面にスリットを設けて構成し、上記分割チムニのスリットにより分割チムニ部を均圧化させた請求項１記載の自然循環型沸騰水型原子炉。 2. The natural circulation boiling water type according to claim 1, wherein the pressure equalizing structure is configured by providing a slit on a plate surface of the divided chimney lattice plate, and the divided chimney portion is pressure-equalized by the slit of the divided chimney. Reactor. 前記均圧化構造は、分割チムニの格子板の板面に連絡孔もしくはスリットをそれぞれ複数設けて構成し、上記分割チムニの連絡孔もしくはスリットにより分割チムニ部を均圧化させた請求項１記載の自然循環型沸騰水型原子炉。 2. The pressure equalizing structure is configured by providing a plurality of communication holes or slits on a plate surface of a divided chimney lattice plate, and the divided chimney portion is pressure-equalized by the communication holes or slits of the divided chimneys. Natural circulation boiling water reactor. 前記均圧化構造は、燃料チャンネル出口を分割チムニの格子板との間に隙間を設けて構成し、この隙間により燃料チャンネル出口において前記燃料集合体間を均圧化させた請求項１記載の自然循環型沸騰水型原子炉。 2. The pressure equalization structure according to claim 1, wherein a gap is provided between the fuel channel outlet and the divided chimney lattice plate, and the pressure between the fuel assemblies is equalized at the fuel channel outlet by the gap. Natural circulation boiling water reactor. 前記炉心上部に設けられる複数の分割チムニは、最外周領域に配置される各分割チムニに１個以上の連絡孔またはスリットを形成し、残りの領域に配置される各分割チムニにも１個以上の連絡孔またはスリットを形成し、最外周領域配置の各分割チムニの連絡孔またはスリットを、残りの分割チムニの連絡孔またはスリットより大きく構成し、チャンネル流量が少なくかつ炉出力が大きくなる周辺部の燃料集合体の間を均圧化させた請求項１記載の自然循環型沸騰水型原子炉。 The plurality of divided chimneys provided in the upper part of the core form one or more communication holes or slits in each divided chimney arranged in the outermost peripheral region, and one or more in each divided chimney arranged in the remaining region The communication hole or slit of each divided chimney in the outermost peripheral area is configured to be larger than the communication holes or slits of the remaining divided chimney so that the channel flow rate is small and the furnace output is increased. The natural circulation boiling water reactor according to claim 1, wherein the pressure between the fuel assemblies is equalized. 原子炉圧力容器の炉心シュラウド内において炉心上部に複数の分割チムニを備え、上記炉心に多数の燃料集合体を装荷した自然循環型沸騰水型原子炉において、
前記炉心シュラウド内に設置された前記分割チムニの領域をチムニ高さ方向に複数に分け、
上部分割チムニ群の角筒状格子板を下部分割チムニ群の角筒状格子板より大きな横断面積を有するように構成し、
前記分割チムニの高さ方向中間部で前記燃料集合体の間の圧力を均一化させたことを特徴とする自然循環型沸騰水型原子炉。 In a natural circulation boiling water reactor equipped with a plurality of divided chimneys in the upper part of the core in the core shroud of the reactor pressure vessel and loaded with many fuel assemblies in the core,
Dividing the region of the divided chimney installed in the core shroud into a plurality of chimney height directions,
The upper divided chimney group square tube lattice plate is configured to have a larger cross-sectional area than the lower divided chimney group square tube lattice plate,
A natural circulation boiling water reactor characterized in that the pressure between the fuel assemblies is made uniform at an intermediate portion in the height direction of the divided chimney. 前記上部分割チムニの角筒状格子板の横断面積を複数の前記下部分割チムニの角筒状格子板の横断面積とほぼ等しく構成した請求項７記載の自然循環型沸騰水型原子炉。 The natural circulation boiling water nuclear reactor according to claim 7 , wherein a cross-sectional area of the square cylindrical lattice plate of the upper divided chimney is substantially equal to a cross-sectional area of the plurality of rectangular cylindrical lattice plates of the lower divided chimney. 原子炉圧力容器の炉心シュラウド内において炉心上部に複数の分割チムニを備え、上記炉心に多数の燃料集合体を装荷した自然循環型沸騰水型原子炉において、
前記炉心シュラウド内に設置された前記分割チムニの領域をチムニ高さ方向に複数に分け、
上部分割チムニ群の角筒状格子板の中心位置を下部分割チムニ群の角筒状格子板の中心位置から横方向にシフトさせ、
前記分割チムニの高さ方向中間部で燃料集合体の間を均圧化させたことを特徴とする自然循環型沸騰水型原子炉。 In a natural circulation boiling water reactor equipped with a plurality of divided chimneys in the upper part of the core in the core shroud of the reactor pressure vessel and loaded with many fuel assemblies in the core,
Dividing the region of the divided chimney installed in the core shroud into a plurality of chimney height directions,
Shifting the center position of the rectangular cylindrical lattice plate of the upper divided chimney group laterally from the central position of the rectangular cylindrical lattice plate of the lower divided chimney group,
A natural circulation boiling water nuclear reactor in which the pressure between the fuel assemblies is equalized at a height intermediate portion of the divided chimney. 前記上部分割チムニ群の各分割チムニは、前記下部分割チムニ群の各分割チムニに対し、この分割チムニの幅方向寸法の範囲内で横方向にシフトさせた請求項９記載の自然循環型沸騰水型原子炉。 10. The natural circulation boiling water according to claim 9 , wherein each divided chimney of the upper divided chimney group is shifted laterally with respect to each divided chimney of the lower divided chimney group within a width dimension of the divided chimney. Type reactor.
JP2005233750A 2005-08-11 2005-08-11 Natural circulation boiling water reactor Expired - Fee Related JP4197696B2 (en)

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